A little-known feature of Aperture is that it will let you compare images side-by-side in the viewer even if they are in different projects or albums. For example, if I have an album of highly-rated images against which I want to compare candidates for five stars, I can open the candidates project alongside the album of highly-rated images and pick one image from each to view simultaneously.

Here is how to do it. Click on one project or album, then Option-click the second one. That will display two grids of thumbnails:

Use Shift W and Option W to get the grid views and the viewer arranged the way you want them. Shift W "rotates" the viewer and the grid and Option W swaps them left/right/top/bottom.

Now select the Compare image by clicking on it and hitting Return, or just option-command click if you want to save a key press. In the picture above the Compare image is the one with the orange border.

As long as the viewer is not in Primary Only mode (put it in multi mode with option U if it is) clicking on another image in the other project will show it as the compared image. Here are the two images displayed together in my viewer:

Clicking on another image or using the arrow keys will change the compared image (white border). Option command clicking on an image or using option with the arrow keys will move the Compare image.

This all works in full-screen mode too, but the Compare image is static and cannot be changed.

Tags: Aperture, Comparing, Browsers